Constraints on inflation revisited: An analysis including the latest local measurement of the Hubble constant

Abstract

We revisit the constraints on inflation models by using the current cosmological observations involving the latest local measurement of the Hubble constant ($H_0=73.00\pm 1.75$ km s ${}^{-1}$ Mpc${}^{-1}$). We constrain the primordial power spectra of both scalar and tensor perturbations with the observational data including the Planck 2015 CMB full data, the BICEP2 and Keck Array CMB B-mode data, the BAO data, and the direct measurement of $H_0$. In order to relieve the tension between the local determination of the Hubble constant and the other astrophysical observations, we consider the additional parameter $N_{\mathrm{eff}}$ in the cosmological model. We find that, for the $\Lambda$CDM+$r$+$N_{\mathrm{eff}}$ model, the scale invariance is only excluded at the 3.3$\sigma$ level, and $\Delta N_{\mathrm{eff}}>0$ is favored at the 1.6$\sigma$ level. Comparing the obtained 1$\sigma$ and 2$\sigma$ contours of $(n_s,r)$ with the theoretical predictions of selected inflation models, we find that both the convex and concave potentials are favored at 2$\sigma$ level, the natural inflation model is excluded at more than 2$\sigma$ level, the Starobinsky $R^2$ inflation model is only favored at around 2$\sigma$ level, and the spontaneously broken SUSY inflation model is now the most favored model.

Comments: 10 pages, 6 figures